In the oil and gas industry it is conventional to mount a rotating blowout preventer or rotating flow head (also known as a rotating flow diverter or rotating flow controller) at the top of a blowout preventer (BOP) stack. The rotating flow head serves multiple purposes including sealing off tubulars moving in an out of the wellbore and accommodating rotation of same. Tubulars can include a kelly, pipe or other drill string component when a top drive is used. The rotating flow head diverts fluids such as drilling mud, surface injected air or gas and produced wellbore fluids into a recirculating or recovery mud line. Typical in-service time numbers in the tens to low hundreds of hours before some part of the operation requires service or other attention including drill bit replacement or other downhole equipment such as motors, turbines and measurement while drilling systems. It is desirable that a rotating flow head last as long as other components and not be the reason operations are interrupted and result in non-productive time (NPT).
As disclosed in U.S. Pat. No. 5,662,181 to Williams et al. and U.S. Pat. No. 6,244,359 to Bridges et al., a variety of means are provided to lubricate the bearing assembly of a rotating flow head. Conventionally, most lubrication means require that a lubricant be injected or pumped into an annulus which houses the bearings to lubricate the bearings. Such lubrication means may require elaborate hydraulic mechanisms and seal arrangements to ensure adequate lubrication.
If the ability to maintain adequate lubrication of the bearings is compromised, the bearings will fail quickly resulting in NPT.
One of the most common sources of premature failure of bearings in current rotating flow head technology is the failure of a seal or seal stack that isolates the wellbore environment from entering the bearing assembly housing.
Reducing operational NPT by maximizing the longevity of the bearings is a key objective for all companies involved in the provision of rotating flow diverter equipment.
There is a need for a sealing system of the bearing assembly which is simple and effective to maximize seal function and prevent premature wear and failure of the bearings.